High-intensity pressure arc lamps of various varieties (for example, metal halide, mercury, Xenon, Excimer, and halogen) and other high-intensity light sources are used in the majority of commercial and industrial applications involving, for example, projection, illumination and displays, inspection, initiation of chemical or biological processes, image reproduction, fluorescence, exposure, sterilization, photopolymer polymerization, irradiation, and cleaning. In each of the applications above, a high irradiation bulb generates a high-intensity broad spectral output of incoherent light that is filtered and spatially modified through the use of complicated optics to allow the emission of a narrow spectral band of light, such as, ultraviolet (UV) light with the proper intensity and spatial properties for the desired application. Unfortunately, conventional high-intensity light sources have a variety of disadvantages, as illustrated in the following examples.
UV light is an effective tool in many production applications in many industries. For example, UV light is used for photopolymer polymerization, a process used widely for various processes such as, printing, lithography, coatings, adhesives, processes used in semiconductor and circuit board manufacturing, publishing, and packaging. UV light, due to its high photon energy, is also useful for molecular excitation, chemical initiation and dissociation processes, including, fluorescence for inspection and measurement tasks, cleaning processes, and sterilization, and medical, chemical, and biological initiation processes, and used in a variety of industries such as, electronics, medicine, and chemical industries. The efficiency and duration of conventional light sources for these applications is extremely low. For instance, 8000 W ultraviolet lamp sources (after filtering) are used in exposure of polymer resists, but they provide only 70 W of power in the spectral range required by the process. Therefore, more efficient semiconductor light sources are needed.
Arrays of semiconductor light sources such as LEDs and laser diodes are more efficient than high pressure light sources and offer advantages over lamps and most other high-intensity light sources. For example, such arrays of semiconductor light sources are four to five times more efficient than that of high-intensity light sources. Other advantages of such semiconductor light source arrays are that they produce a far greater level of spectral purity than high-intensity light sources, they are more safe than high-intensity light sources since voltages and currents associated with such diodes are lower than those associated with high-intensity light sources, and they provide increased power densities since due to smaller packaging requirements. Furthermore, semiconductor light source arrays emit lower levels of electromagnetic interference, are significantly more reliable, and have more stable outputs over time requiring less maintenance, intervention, and replacement than with high-intensity light sources. Arrays of semiconductor light sources can be configured and controlled to allow individual addressability, produce a variety of wavelengths and intensities, and allow for rapid starting and control from pulsing to continuous operation.
None of the prior art discloses a semiconductor light source that can be adapted for a variety of applications and/or provide the high power densities required by a variety of applications.